1. Field of the Invention
Embodiments of the present invention relate generally to optical communication systems and components and, more particularly, to a wavelength selective switch.
2. Description of the Related Art
In a wavelength division multiplexing (WDM) optical communication system, information is carried by multiple channels, each channel having a unique wavelength. WDM allows transmission of data from different sources over the same fiber optic link simultaneously, since each data source is assigned a dedicated wavelength component, or channel. The result is an optical communication link with an aggregate bandwidth that increases with the number of wavelengths, or channels, incorporated into the WDM signal. In this way, WDM technology maximizes the use of an available fiber optic infrastructure; what would normally require multiple optic links or fibers instead requires only one.
In WDM optical communication systems, it is often necessary to add, drop, or attenuate individual wavelength channels in a WDM signal. These functions can be achieved by an optical switching device, which directs an input light beam to one of multiple output optical paths. For example, in a 1×2 optical switching device, an input light beam enters through one input fiber and is directed to one of two output fibers. All optical energy of the input beam may be directed to a single output fiber or a portion of the optical energy may be directed to each output fiber, depending on the purpose of the optical switching device, i.e., simple switching vs. broadcasting or attenuation/equalization. The input light beam so directed may be a complete WDM optical signal or an individual wavelength channel of a WDM optical signal. An optical switch configured to perform such optical switching on a per wavelength channel basis is referred to as a wavelength selective switch (WSS), and is typically capable of switching any wavelength channel at the input fiber to either of the output fibers.
More complicated optical switching schemes than 1×2 switching are also commonly used in optical communication systems, such as 1×N switching, which can be realized by configuring multiple 1×2 switching devices in series and/or in parallel, or by incorporating 1×N functionality into a single optical switching device. Similarly, optical switching devices that are configured to switch each of the wavelength channels of multiple input fibers to any of the N output fibers can be constructed from a plurality 1×N devices. 1×N optical switching devices for WDM communication systems are, however, quite complex, and include active and passive optical elements that must be manufactured and aligned to high tolerances for proper operation. Consequently, producing such as device by arraying a plurality of 1×N optical switching devices is generally undesirable.